The present invention relates to a device for automotive vehicles with traction control for controlling the drive power of a vehicle engine when control action takes place as a function of electric signals derived from the wheel rotational behavior. The device comprises a hydraulically actuatable control apparatus interposed into the path of force transmission from a drive control pedal, such as the accelerator pedal, to a control member of the vehicle engine. The control member can be the throttle-flap of an internal-combustion engine, the adjusting lever of a spark-ignition engine or the like. The control apparatus is connectable by way of multidirectional valves to an auxiliary-pressure source and to a pressure-compensating reservoir and a piston displaceable by the auxiliary pressure.
Devices of this type for traction slip control are known. These devices are combined with anti-lock systems because the brake system can also be used for controlling the traction slip for the purpose of traction control in an initial period prior to the intervention in the driving engine, i.e., prior to the reduction of the drive power. Further, component parts of the anti-lock system, for instance the wheel sensors, the electronic circuits for processing the signals as well as the auxiliary-energy supply system may likewise be employed for traction control.
German published patent application 30 21 116 describes a combined anti-lock and traction control system wherein a control apparatus is inserted into the linkage from the accelerator pedal to the throttle-flap of the vehicle engine for the purpose of traction control. In this case, the control apparatus is a drag link which contains a piston guided in a cylinder in opposition to the force of a compression spring and displaceable by the introduction of auxiliary pressure. The throttle-flap is opened by pressure by way of a linkage in which the drag link is interposed. In the presence of excessive traction slip, auxiliary pressure is hydraulically introduced, thereby the length of the drag link and thus the entire length of the linkage is reduced. As a result, resetting of the throttle-flap and hence a reduction of the drive power of the vehicle engine is accomplished. It is a disadvantage, among others, that the resetting of the throttle-flap can be cancelled at least partially by further depression of the accelerator pedal.
Another known device for the slip limitation during traction is equipped with an adjustable stop for the accelerator pedal (German published patent application 33 37 664). In this event, a piston guided in a cylinder is also used as control apparatus, which piston limits the depression of the accelerator pedal and resets the pedal, respectively, by the introduction of pressure. A bellows serves as an adjustable pedal stop into which hydraulic oil can be introduced in the event of excessive traction slip. It is a shortcoming that the resetting force is transmitted in a full extent onto the accelerator pedal, annoying to the driver when quick-responding systems are used. Instead of the hydraulically actuatable devices, it is also possible to use an electric motor as control apparatus.
It is the object of the present invention to overcome the described disadvantages of the known devices and to provide a device for controlling the drive power of a vehicle engine, wherein the reaction of the control on the pedal is at least largely damped and which, on commencement of the control, will not react on further depression of the pedal. Moreover, the throttle-flap or the control member is instantaneously reset in the event of release of the accelerator pedal or reduction of the actuating force applied on the accelerator pedal.